1. Field of the Invention
The present invention relates to novel amino acid a derivative, N.sup..alpha. -tert-butoxycarbonyl-N.sub..epsilon. -(N-bromoacetyl-.beta.-alanyl)-L-lysine (BBAL), for use in solid-phase or solution-phase peptide synthesis for introducing a side-chain bromoacetyl group at any desired position in a peptide sequence. The bromoacetyl group is subsequently used for the preparation of cyclic peptides, peptide conjugates and peptide polymers. Such peptide derivatives are useful in preparing potential peptide immunogens, vaccines and therapeutics, and for substances such as peptides linked to polymers, plastics, enamels and ceramics.